50Hz? What sub do you have? That seems pretty poor for any sub other than a $30 PC 2.1 system. If you listen at very low levels without Dynamic EQ engaged, that might be part of the reason, but honestly, something seems wrong.
As far as theater, you're talking to the wrong guy. I am 95/5 HT/music and if you are talking HT content and not just TV (sit-com, news, etc with no LFE) I am probably more like 99/1!
For music, I am happy with dual 8" sealed subs (Velodyne VMS-8/Photon 8) once room gain and Audyssey are in play, but you can see that +/-3dB puts F3 around 30Hz. By your description, I would not guess you have this much bass?:
Switching to a larger, more capable sub gets me a better HT experience. Part of it may be that these are topping out on explosions, etc. My subjective perception is that it is also deeper bass, but I have never attempted to listen for certain pitches. Certainly, there is quite an obvious visceral difference when playing something like the intro to "Live, Die, Repeat" (which is an "unsettling" experience). Understand that my most capable sub for HT is a pair of Rythmik E15HP's which I love, but many here would scoff at them as being "lightweight". I have yet to hear a ported sub that sounds as good, but I need to revisit a comparison against TheWarrior's PC12-plus's now that he has mini-DSP'ed them.